The Magnetic flux Φ passing through a given area A is the product of the magnetic flux density B and the area it passes through. Φ = BA, where the area A is perpendicular to the field. The magnetic flux that links a coil of N turns is called the magnetic flux linkage and is given by NΦ or NBA. The unit is the weber (Wb)Faraday's Law of electromagnetic induction states that the induced emf in a circuit is equal to the rate of change of flux linkage through a circuit.ε = -NδΦ/δt = change of flux linkage per second. The minus sign represents the induced emf acting in a direction to oppose the change that causes it.